In a load-lifting operation using a forklift, interferences between a fork and a load or a pallet to be lifted need to be avoided. In a forklift described in Japanese Patent Application Publication No. 2005-89013, a reflective optical sensor detects upper and lower ends of an opening of a pallet. Then, a clearance between an upper surface of a fork and the upper end of the opening of the pallet and a clearance between a lower surface of the fork and the lower end of the opening of the pallet are calculated, and a fork position is adjusted so that these clearances take appropriate values.